1. Field of the Invention
This invention relates to a post-ashing treating liquid composition and a process for treatment therewith. More particularly, the invention relates to a treating liquid composition which exhibits an excellent performance in treating a substrate having been dry-etched through a photoresist pattern formed thereon using as a mask pattern, followed by ashing, and it also relates to a process for treatment with the treating liquid composition. The treating liquid composition of the invention effectively removes residues, such as a modified or deteriorated photoresist film and metal depositions from a substrate with fine photoresist patterns formed thereon, which are remained or built up during etching and subsequent ashing. Moreover, it effectively protects from corrosion metal wiring, metal (oxide) layers, metal insulating layers deposited by CVD on the substrate. It also prevents organic SOG (spin on glass) layers from damage, such as poisoned via. The present invention is appropriately applicable to the production of semiconductor devices such as Ics, LSIs and liquid-crystal panel devices.
2. Description of Related Art
Semiconductor devices such as ICs and LSIs as well as liquid-crystal panel devices are fabricated by a process comprising the following steps: forming a conductive metallic layer or an insulating layer such as an SiO.sub.2 film by CVD onto a substrate; applying a uniform photoresist layer over the metallic or insulating layer; selectively exposing the applied photoresist layer to light and developing the exposed layer to form a photoresist pattern; selectively etching the above-mentioned conductive metallic layer or insulating layer through the photoresist pattern as a mask pattern to form a fine-line circuit; and stripping away the remaining photoresist layer which is not necessary any longer. For the removal of such an unnecessary photoresist layer, a stripping agent that contains an organic amine as an essential ingredient, such as, for example, monoethanolamine, is commonly used today, because of its effectiveness in removing photoresists, and further for safety reasons.
As the metallic layer, use may be made of various ones, for example, aluminum (Al); an aluminum alloy (Al alloy), such as aluminum-silicon (Al--Si), aluminum-copper (Al--Cu) or aluminum-silicon-copper (Al--Si--Cu); titanium (Ti); a titanium alloy (Ti alloy), such as titanium nitride (TiN) or a titanium-tungsten system (TiW); tantalum (Ta); tantalum nitride (TaN); tungsten (W); or tungsten nitride (WN). One or more of such metallic layers are formed onto the substrate.
With the recent tendency toward high-density integrated circuits, dry etching enabling fine etching with a higher density has become the major means. Also, it has been a practice to employ plasma ashing to remove the unnecessary photoresist layers remained after etching. After etching, followed by ashing, residues of modified photoresist films and other components remain as referred to "veil" or "fences" on the bottom or side wall of patterned grooves. In addition, etching of metallic layers builds up metal depositions. Such residues and depositions should be completely removed so as to keep good yields in the production of semiconductors.
These residues and depositions vary in composition depending on the type of the etching gas employed, the ashing conditions, the type of the metallic layers and insulation layers formed on the substrate, the type of the photoresist employed, etc. In recent years, attempts have been made to improve semiconductors by various methods. As a result, the treating conditions in each step become strict and a great variety of metals, insulation layers and photoresits are employed therefor. Consequently, the residues and depositions become complicated, which make it difficult to identify those compositions. Under these circumstances, no satisfactory treating solution and treating method have been known so far.
In addition, a common way used recently to planarize the multilayer interconnected substrate is by forming one or more of thick organic SOG layer(s) on the substrate in place of conventional etch-back process. However, said organic SOG layer is liable to be corroded by water present in treating liquid compositions. Thus, there is an increasing demand for a treating liquid composition, which does not cause damage to the organic SOG layer.
There have been several solutions used for removal of modified photoresist films and for treatment after ashing. They are exemplarily disclosed in Unexamined Published Japanese Patent Application (Kokai) Nos. 202052/1996, 197681/1997, and 73348/1989.
Kokai No. 202052/1996 teaches a solution for resist removal that contains hydrofluoric acid, a salt thereof with a base free from metal ions, a water-soluble organic solvent, and an anticorrosive agent. Owing to hydrofluoric acid incorporated therein, the solution removes efficiently remove modified photoresist films and metal depositions remaining after ashing. However, it does not prevent satisfactorily corrosion on the apparatus near the solution feeder, damage to the organic SOG layer, and corrosion on metal layers and metal oxide layers.
Kokai No. 197681/1997 teaches a solution for resist removal which contains a salt of hydrofluoric acid with a base free from metal ions, and a water-soluble organic solvent, which has a pH of 5-8. This solution is an improved one of the solution disclosed in the above Kokai No. 202052/1996. The improvement is achieved by reducing the amount of hydrofluoric acid and hence adjusting the pH in the solution properly. Therefore, this solution corrodes less metal layers, metal oxide layers, and nearby-placed apparatus, and it damages less the organic SOG layer. However, it is not satisfactorily effective in removing residues left after fine patterning on substrates.
Kokai No. 73348/1989 teaches a solution for resist removal that contains an organic stripping solution and acetylene alcohol. This solution is for the use of removing photoresist during fabrication that does not include ashing process. It therefore cannot be used to remove resist residues such as modified photoresist film and metal depositions remaining after etching followed by ashing under severe conditions in fine patterning on substrates.
In view of the fact that the conventional treating liquid composition poses contradictory problems, that is, it corrodes metal layers and metal oxide layers and it damages the organic SOG layer if the content of hydrofluoric acid is high, while it does not remove residues completely if the content of hydrofluoric acid is low, the present inventors carried out extensive studies to minimize the effect of hydrofluoric acid. As a result, it was found that the problem is solved if a specific compound is added to a treating liquid composition containing hydrofluoric acid, a salt thereof with a base free from metal ions, and water. The present invention was completed on the basis of the findings.